1. Field of Invention
This invention relates to ice skating blades, specifically to an improved method of sharpening.
2. Description of Prior Art
Skate blades used for ice hockey, figure, free style and dance, etc., are made from hardened and tempered steel having sharp inside and outside edges separated by a concavity. With use, these edges become dull and the concavity which supports the skater's weight, loses its smoothness and shape thus degrading the performance of the skater.
Heretofore it was common practice to restore these edges and the concavity using a grinding machine designed for this purpose. Such machines generally utilize a flat disc-shaped grinding wheel mounted on a vertical shaft, rotating at high speed. This in turn is mounted to a flat steel table such that the grinding wheel is several inches above the surface of the table. To grind the concavity, a suitable radius for each type of skate must be formed on the rim of the grinding wheel using a radius forming tool. The skating blade with boot attached is clamped on its side to a steel block which slides easily in any direction over the table surface. The center line of the skate blade runs parallel with the surface of the table and the grinding wheel is adjusted to a suitable level to match the center line of the blade.
Using a continuous sweeping motion, the operator then moves the skate blade against the grinding wheel, thus restoring the concavity and sharpening both edges. Some machines have two stations so that a medium grit and a fine grit grinding wheel are available. Other machines use similar grinding methods.
New skate blades are manufactured with very specific curvatures to enable a skater to perform intricate maneuvers on the ice. Undulations and change of curvature of the skate blade will occur with each resharpening. Operator skill and experience is critical in attempting to minimize these distortions.
On some machines a template may be used to restore the curvature. However, this method is seldom used since a template for each size and type of skate blade is required. Also a considerable amount of metal removal is often necessary to restore the original curvature.
To grind the concavity a suitable radius for each type of skate must be formed on the edge of the grinding wheel using a special diamond tool.
During the sharpening operation the grinding wheel, rotating at high speed, heats the skate blade. This in turn permanently softens the edges being sharpened resulting in the need for more frequent regrinds since softened edges become blunt more rapidly than hardened edges with use. Such heating could be avoided using a cutting fluid, however skate grinding machines are designed to operate "dry".
Some disadvantages of the above method of sharpening skate blades are listed below:
OPERATOR SKILL REQUIRED. The operator must have a high degree of skill in attempting to maintain an even pressure and steady traverse without bounce while pressing the skate blade against the spinning grinding wheel.
DISTORTION. Regardless of operator skill, undulations and curvature distortions do occur, this being cumulative with future regrinding.
HIGH COST. Different blades require different concavity radii. An expensive diamond tool is used to form whichever radius is needed on the edge of the grinding wheel. During use, further dressing of the grinding wheel becomes necessary due to loading and glazing thus reducing the grinding wheel diameter to the point where frequent replacements become necessary.
SOFTENS EDGES. Grinding without using cutting fluid causes severe heating, particularly at the edges of the blade. This results in softening of these hardened steel edges which now blunt rapidly with use, leading to more frequent resharpenings.
ROUGH SURFACE FINISH. A polished surface on the concavity of the blade is desirable for low skating friction (the total weight of the skater is concentrated on a very small area of this surface). However when using a fine grit or polishing wheel without the use of cutting fluid, severe softening of the edges will occur. Hence a relatively coarse finish instead of a mirror finish must be tolerated.
DIFFICULTY IN CHANGING GRINDING WHEEL RADIUS. The correct concavity radius must be formed on the grinding wheel using a radius fixture with a diamond tool. This procedure is time consuming requiring expertise. The fixture containing the diamond tool must be adjusted to the required radius prior to shaping the grinding wheel. It is not practical to have a set of grinding wheels each with a different peripheral radius since the wheel, when mounted, will not run precisely true, hence the need to be recontoured after mounting.
LACK OF PORTABILITY. Most machines are too heavy and cumbersome to transport easily (e.g. in the trunk of a car).
DEGRADATION OF SKATING ABILITY. Skaters usually delay sharpening until a regrind is absolutely necessary since a potential setback in skating performance is anticipated due to the change in curvature as a result of sharpening.
SKATING BLADE REPLACEMENT. By design the skate blade has a specific curvature. Towards the front the curvature becomes tighter (the rocker). This transition is used by the skater to execute 3-turns, counters, etc., and when flattened due to regrinding, the skater must compromise her ability with an increased danger of accident. Also excessive loss of metal often occurs at the heel end of the skate blade posing a danger to the skater of falling backwards. A common solution is the purchase of new blades.
PROTECTIVE EQUIPMENT REQUIRED. When grinding skate blades, the operator must wear both goggles and breathing mask to protect him from high velocity metal particles and the inhalation of metal dust.